In a spectacle frame shape measuring apparatus for measuring a shape of a spectacle frame, etc., a measurement error is generated due to long-term use, and such a measurement error is generally calibrated by using a calibration jig.
Such a calibration jig (reference frame) 100 is described in Patent Document 1, and as shown in FIG. 9, reference holes 102 being through holes are formed through a metal plate 101 of the calibration jig corresponding to the plan-view shape of rims of a spectacle frame. The inner circumferential surfaces 103 of the reference hole 102 is traced with the tip portion of a measuring probe 104 of a spectacle frame shape measuring apparatus being a measurement object, with the tip portion of the measuring probe 104 kept in contact with the inner circumferential surfaces 103. A measurement error of the spectacle frame shape measuring apparatus being a measurement object is calculated by comparing measurement data measured by the way in which the measuring probe 104 of the spectacle frame measuring apparatus being a measurement object traces the inner circumferential surface 103 of the reference hole 102 in the calibration jig 100 with reference data obtained in advance by accurate measurement of the inner circumferential surface 103 of the reference hole 102 in the calibration jig 100.    Patent Document 1: Unexamined Japanese Patent Application Publication No. H4-13539